Wave guide system



J y 11, 1950. I c. A. MARTIN 2 51 WAVE GUIDE SYSTEM Filed May 14, 194711/045 POI/W5 r "f I7 5 ,7 5 l8 5 INVENTOR.

CHARLES A. MARTIN" Patented July 11, 1950 WAVE SYSTEM Charles A. Martin,Rocky Point, N. Y., asslgnor to Radio Corporation of America, acorporation of Delaware Application May14,1947, Serial No. 748,058

The present invention relates to a system for combining a number ofmicrowave radio waves into a single wave guide or electromagnetic hornstructure.

' An object of'the presentinventionis to provide a combiningstructure-for introducing a number of microwave radio waves into asingle wave guide.

Another object of the present invention is the provision of a combiningsystem as aforesaid in which each wave propagated in the wave guide isof thedominant type and, therefore, is more suitable for'immediateradiation by electromagnetic hornor other wave directive structure.

Another object of the present invention is to provide a combining systemfor high frequency radio waves in whichthefeed point of each wave doesnot disrupt the continuity of the wave guide system for any other wavein the guide. Another object of the present inventionis ,the provisionof a combining system as aforesaid 14 Claims. (Cl. 178-44) point as faras all other waves, existing at the feed point in the wave guide, areconcerned. Moreover, the adjustments necessary to regulate the rejectionbands are substantially independent of those of the pass band and ofeach other, and,

therefore, the tuning of the system is simple and straightforward.

- While, for convenience, the foregoing brief description and thefollowing detailed description are based on the assumption that thepresent invention is to be used for coupling a plurality of sources ofhigh frequency energy to a high im-.- pedance horn antenna or load, itshould be clearly understood that my invention is not limited thereto,but may also be used to couple a plurality of separateloads or receiversto a wave guide carrying a number of separate high frequencywaveswherein the energy from each source is prevented from entering thesource, of anyother wave.

Still another. object of the. present invention is the provision of amicrowave combining system in which each feed system is capableoffeeding the .wave guide with arelatively wide 'ba nd of frequencies. I

Another object of the present invention is the provision of a microwavecombining system in which the necessary adjustments may be simply madeand are straightforward in character.

The basic principle uponrwhich the present invention is based is that noreal power of an electromagnetic wave will propagate along awave guidehaving lateral dimensions less than a certain. critical magnitude: inother words, a wave guide inherently acts as a high passfilte'r. Thus,the present. invention contemplates utilizing a tapered wave guidesection with the individual frequencies beingfed into the tapered waveguide at points such that the, waves may propagate only in one directionalong the guide; that is, in the direction of increased dimensions- Trapcircuits are provided so that the entrance points of the lower frequencywaves are effectively short In the system of this disclosure a wide passband is provided ineach feed system so that ,a number of signals ofsmall wavelength dif-.

ferences may be'introduced at each feedpoint .of the wave guide by theusual practice of using filters. In addition, the remaining impedance=-function of each feed system is controlled to provide 1 an effectiveshort circuit acrossv the. feed 2 4, circuited for high frequency wavesoriginating in thesmaller portions of the guide system.

or to a horn antenna receiving, any one of a number of separate waveswithout adjustment or a number of waves simultaneously.

The present invention will be more fully understood by reference to thefollowing detailedvdescription which is accompanied by a drawing inwhich:

Figure 1 illustrates in perspective and partly in section an embodimentofv the present invention;

Figure 2 illustrates in perspective a modification of a portion of thestructure of Figure 1, while Figure 3 illustrates a further modificationthereof.

Referring now to Figure 1 there is shown a tapered wave guide '5. Threesources of high frequency energy A, B, and C of progressively lowerfrequency are shown. For the purpose of explaining the present inventionbut with no intent of limiting the invention to the particulardimensions suggested, let us assume that the wavelengths bearthefollowing relationship where AA,

is, and w are the wavelengths of three sources:

ie=1nsie=sic Now, at the point where the source A feeds its energyintowave guide 5, the dimension a of the waveguide is such that waveshaving a wavelength equal to that of source A may be propagated alongthis portion of the guide. The guide 5 expands in its dimensions untilat the point Where wave guide section 3 joinsit, the width 1) permitsthe propagation ofnot only waves having a length equal to that of sourceA but also waves having a wavelength equal to thatof source B. Also, ata still largerpart of wave guide 5 where the dimension 0 is large enoughto permit the propagation of all three waves, waves from source .Q-areintroduced into the waveguideby the intermediate section 4 throughthroat 10. The following table gives the numerical relationship betweenthese dimensions and certain other dimensions which will later bedescribed:

It will be noted that the dimensions a, b, c, d, e, f, q and r are suchthat any real power of any of the waves is prevented from propagatingback to the feed point of any other wave of shorter wavelength and suchthat electromagnetic waves of the dominant type and dominant type onlyare allowed to propagate from left to right in the figure.

The branch wave guide 4 coupling source C to the main wave guide 5 willnow be described in detail. Trap circuit elements l5 and I6 branchingfrom the branch guide 4 prevent coupling of sources A and B into sourceC and also maintain the continuity of the main wave guide 5 at junctionIn as far as the waves of sources A and B propagated in 5 are concerned.

The branch l6 has three parallel portions 6, 1 and 8 closed by plungersll, l2 and [3 respectively. These three portions each have lateraldimensions a large enough to allow energy of source A to enter them butsmall enough to exclude energy from sources B and C. The position of theplungers H, l2 and i3 within the parallel guide sections may be variedto tune the circuit elements 6, 1 and 8 so that their effectiveimpedance at the junction with the guide 4 may be made substantiallyinfinite at the wavelength M. This effect may be obtained if, forexample, the dimensions is and e are made approximately equal to aquarter of the guide wavelength of the source A. Now, by suitablychoosing the dimension 7', the distance between element [6 and thejunction of guide 4 and guide 5, the effective high impedance at thethroat of guide I6 is converted at the throat ID to a short circuiteffectively for waves of the wavelength of source A. Since the i.

dimension a is less than Ma and also less than /2 M3, the presence ofthe element l5 has but a small effect on waves of the sources B and Cwhich may exist in the wave guide 4.

The branch [5 has the same function in reard to waves of source B thatIt has for waves of source A. The branch wave guide section of width bis large enough to admit energy of source B but small enough to excludeenergy of source C. The plunger l4 may be varied to tune the circuitelement [5 so that the effective impedance at the junction 9 issubstantially infinite at the wavelength M3. Then by suitably choosingthe dimension n, the distance between the branch I5 and the guide 5, theeffective high impedance at the throat of I5 is converted at the throatI!) to a short circuit effectively for waves of the wavelength of sourceB. In'addition to the abovedescribed action on waves of source B, l5 maybe used to have a favorable effect on waves from source 0. This isaccomplished by constructing 15 so that it is composed of a section ofwidth (the width of the guide 4) extending from wave guide 4 a distancep. This distance p may be selected so that this section of l at leastpartially compensates for the effects on waves of source C of the waveguide discontinuities at l0, 6, 1 and 8.

Trap 26 on wave guide 3 functions similarly to on 4. The dimensioning of26 is such that the smaller wave guide section of width a preventsenergy of source A entering guide 3 and the larger section of width b atleast partially compensates for the discontinuity at the junction of 3and 5.

While the elements described above may be classified as the essentialelements of the system various modifications in dimensioning andconstruction of the elements may be necessary depending mainly on thewavelengths and the bandwidth of wavelengths which are to betransmitted. For example, it may be desirable to obtain a more favorableimpedance match to the source C over a wide bandwidth by using such wellknown devices in the wave guide 4 as diaphragms 0r tuning screws. As afurther example, supposing source A is to transmit a wide bandwidth ofsignals, it may be desirable to use an additional element such as l6suitably positioned along 4. Then by varying the length of the variousparallel portions of 16 and the added element a greater bandwidth ofwavelengths near M may be prevented from entering wave guide 4.

A modified system is shown in Figure 2 in which the main wave guide 5 ofFigure 1 is replaced by discontinuous sections in the form of hollowrectangular prisms 5, 5" and 5" joined by tapered or truncated pyramidalsections I1 and I8. Under some circumstances this form of constructionmay be desirable in that it provides more freedom in the longitudinalpositioning in the feed point of branch guide 4. Losses in the main waveguide may also, under some circumstances, be reduced by the increase inthe taper angle in the sections l1 and i8. Except as noted the structureof the modification of Figure 2 is the same as that described above withreference to Figure 1.

A further modification is shown in Figure 3 wherein the branch waveguides 3 and 4 of Figure 2 are bent at right angles at their junctionpoint with the guides 5" and 5" in order to run parallel thereto. Thejunction between guide 3 and 5", now it will be seen, takes the form ofa right angle corner. The planes 2! at the corners improve the matchbetween the two merging wave guides and reduce reflections which wouldotherwise occur at a sharp right angle bend.

While I have illustrated a particular embodiment of the presentinvention, it should be clearly understood that it is not limitedthereto since many'modifications may be made in the several elementsemployed and in their arrangement and it is therefore contemplated bythe appended claims to cover any such modifications as fall within thespirit and scope of the invention.

What is claimed is: v

1. A wave guidesystem including a main guide adapted to be coupled to aload circuit at one end and having a source of high frequency energycoupled to the other end, said guide having increasing transversedimensions in the direction toward said load, said dimensions at saidother end being only large enough to transmit energy of the frequency ofsaid source, and branch guides, each having a source of energy of lowerfrequency than said first mentioned source coupled to one end, saidbranch guides being coupled to said main guide at points therealongwhere its dimensions become large enough to transmit said lowerfrequency energies.

2. A wave guide system including a main guide adapted to be coupled to aload circuit at one end and having a source of high frequency energycoupled to the other end, said guide having increasing transversedimensions in the direction toward said load, said dimensions at saidother end being only large enough to transmit energy to said main guideat points therealong where its dimensions become large enough totransmit said lower frequency energies, each of said branch guideshaving waveguide elements coupled therewith to present a negligibleimpedance to the energy within said branch guide and being adjusted topresent a substantially short circuit at the junction of said branchguides and said main guide to energy from sources of higher frequency.

, 3. A wave guide system according to claim2 in which said main guidehas alternate rectangular hollow prismatic sections and hollow truncatedpyramidal sections, said branch guides being coupled to said main guidein said prismatic sections.

4. A wave guide system including a main guide adapted to be coupled to aload circuit at one end and having a source of high frequency energycoupled to the other end, said guide having increasing transversedimensions in the direction toward said load, said dimension at saidother end being only large enough to transmit energy of the frequency ofsaid source, a first branch guide having a source of energy of lowerfrequency than said first source coupled thereto and a second branchguide having a source of energy of lower frequency than either of theother of said sources coupled thereto, said branch guides being coupledto said main guide at points along said guide where its transversedimensions are large enough to transmit energy from the source coupledthereto.

5. A wave guide system including a main guide adapted to be coupled to aload circuit at one end and having a source of high frequency energycoupled to the other end, said guide having'increasing transversedimensions in the direction toward said load, said dimensions at saidother of the frequency of said source, a first branch guide having asource of energy of lower frequency than said first source coupledthereto and a second branch guide having a source of energy of lowerfrequency than either of the other of said sources coupled thereto, saidbranch guides being coupled to said main guide at points along saidguide where its transverse dimensions are large enough to transmitenergy from the source coupled thereto, said first branch having afurther branch guide coupled thereto, the transverse dimensions of saidfurther guide being such as to be responsive only to energy from saidfirst-mentioned source and having a length at which a low impedance ipresented at the junction between said main guide and said first branchguide.

6. A wave guide system according to claim 5 in which said main guide'hasalternate rectangularhollow prismatic sections and hollow truncated .6of the frequency of said source, a first branch guide having a source ofenergy of lower frequency than said first source coupled thereto and asecond branch guide having a source of energy of lower frequency thaneither of the other of said sources coupled thereto, said branch guidesbeing coupled to said main guide at point a ong said guide where itstransverse dimensions are large enough to transmit energy from thesource coupled thereto, said first branch having a further branch guidecoupled thereto, the transverse dimensions of said further guide beingsuch as to be responsive only to energy from said firstmentioned sourceand having such length that at the junction between said main guide andsaid first branch guide a low impedance shunt is presented, said secondbranch guide having further branch guides coupled thereto, said furtherbranch guides having transverse dimensions to render them responsiveonly to energy from said first and second sources of energy and havinglengths at which a low impedance is presented to energy from said firstand said second sources at the junction of said main guide and saidsecond branch.

8. A wave guide system including a main guide adapted to be coupled to aload circuit at one endand having a source of highfrequency energycoupled to the other end, said guide having increasing transversedimensions in the direction toward said load, said dimensions at saidother end being only large'enough to transmit energy of .the frequencyof said source, a first branch guide having a source of energy of lowerfrequency than said first source coupled thereto and a second branchguide having a source of energy of lower frequency than either of theother of saidsources coupledv thereto, said branch guides being coupledto said main guide at points along said guide where its transversedimensions are large enough to transmit energy from the source coupledthereto, said first branch having a further branch guide coupledthereto, said further branch guide being so arranged that at thejunction between said main guide and said first branch guide a lowimpedance is presented to energy from said first-mentioned source.

9. A wave guide system according to claim 8 in which said main uide hasalternate rectangular hollow prismatic sections and hollow truncatedpyramidal sections, said branch guides being coupled to said main guidein said prismatic sections.

10. A wave guide system including a main guide adapted to be coupled toa load circuit at one end and having a source of high frequency energycoupled to the other end, said guide having increasing transversedimensions in the direction toward said load, said dimensions at saidother end being only large enough to transmit energy of the frequency ofsaid source, a first branch guide having a source of energy of lowerfrequency than said first source coupled thereto and a second branchguide having a source of energy of lower frequency than either of theother of said sources coupled thereto, said branch guides being coupledto said main guide at points along said guide where its transversedimensions are large enough to transmit energy from the source coupledthereto, said first branch having a further branch guide coupledthereto, said further branch guide being so arranged that at thejunction between said main guide and said first branch guide a lowimpedance is presented to energy from said: firstem'entioned source,said secondibranch guidehaving further branch guides coupled thereto;said further branch guides being so arranged thatrat-the junction of.said main guide and" said branch. guide a low impedance to energy from:said first and second sources is presented;

11. A wave guide-systemincluding a main guide adapted. to bev coupled toa load circuit at oneend and having asource ofhigh frequencyenergycoupled: to the other end, said guidehaving increasing transversedimensions in the direction toward. said. load, said dimensions at saidother end being only large enough to transmit energy or the frequency ofsaid source, a first branch guide having a. source of energy of lowerfrequency than said first source coupled thereto and a second branch.guidehaving a source of energy of. lower frequency than either of theother of said sources coupled thereto, said branch guides being coupledto said main guide at points along said guide where its transversedimensions, are large enough to transmit energy from the source coupledthereto, said first branch having coupled thereto a wave guide elementhaving dimensions at which a high. impedance is presented to energy fromsaid first source and to the energy from the source associated with saidguide, the spacing between said wave guide element and the junctionbetween said main guide and said first branch having a value at which. alow impedance across said branch is presented to energy from said firstsource.

12. A wave guide system including a main guide adaptedto be coupled to aload circuit at one end and having a source of high frequency energycoupled to the other end, said guide having increasing transversedimensions in the direction toward said load, said dimensions at saidother end being only large enough to transmit energy of" the frequencyof said source, a first branch guide having a source of energy of lowerfrequency than said first source coupled thereto and a second branchguide having a source of energy of lower frequency than either of theother of said sources coupled thereto, said branch guides being coupledto said main guide at points along said guide where its transversedimensions are large enough to transmit energy from the source coupledthereto, said first branch having coupled thereto a wave guide elementhaving dimensions at which a, high impedance is presented to energy fromsaid first source and the energy from the source associated with saidguide, the spacing between said wave guide element and the junctionbetween said. main guide and said first branch having a value at which alow impedance across said branch is presented to energy from said firstsource, said second branch having coupled thereto a number of highimpedance wave guide elements spaced from the junction between said mainguide and second guide to present a low impedance across said secondbranch to energy from said first sources and from the second of saidsources.

13. A wave guide system according to claim 12 in which said main guidehas alternate rectangular hollow prismatic sections and hollow truncatedpyramidal sections, said branch guides being coupled to said main guidein said prismatic sections.

14. A wave guide system including a wave guide, a plurality of sourcesof high frequency energy of different frequencies coupled to said waveguide at spaced points along the longitudinal axis of said vave guide,said wave guide having dimensions transversely of said longitudinal axisbetween said spaced points at which energy from a source of lowerfrequency is prevented from flowing back over said wave guide toward asource of higher frequency.

CHARLES A. MARTIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,129,669 Bowen Sept. 13, 19382,407,318 Mieher Sept. 10, 1946 2,429,640 Mieher Oct. 28, 1947 2,432,093Fox Dec. 9, 1947 2,441,574 Jaynes May 18, 1948

